What constitutes a high maximal respiratory rate (MRR) indicative of tachypnea during an exercise stress test?

From the Guidelines

A maximal respiratory rate above 40 breaths per minute is generally considered high during an exercise stress test, as indicated by the World Health Organization's (WHO) definition of tachypnea in children 1. For most adults, a maximal respiratory rate between 30-40 breaths per minute is typical at peak exercise. Rates exceeding 40 breaths per minute may indicate very high intensity exercise, reduced respiratory efficiency, or potential underlying cardiopulmonary issues. It's essential to consider factors like age, fitness level, and type of exercise when interpreting maximal respiratory rates. Younger, highly trained athletes may achieve higher rates without concern, while older adults or those with lung conditions may reach lower maximal rates. Some key points to consider when evaluating maximal respiratory rates include:

• Age: Maximal respiratory rates can vary significantly with age, with younger individuals tend to have higher rates 1
• Fitness level: Highly trained athletes may achieve higher maximal respiratory rates due to increased respiratory efficiency
• Type of exercise: Different types of exercise can affect maximal respiratory rates, with high-intensity exercises tend to result in higher rates When interpreting exercise test results, the maximal respiratory rate should be considered alongside other parameters like oxygen uptake, heart rate, and blood pressure. A high respiratory rate alone doesn't necessarily indicate a problem if other measures are within normal ranges. If you consistently reach very high respiratory rates during exercise, especially if accompanied by excessive shortness of breath or chest discomfort, consult a healthcare provider for a thorough evaluation of your cardiopulmonary function, as tachypnea can be a predictor of underlying conditions, such as pneumonia in children under 2 years of age 1.

From the Research

Maximal Respiratory Rate (MRR) Indicative of Tachypnea

• A high maximal respiratory rate (MRR) is often considered indicative of tachypnea during an exercise stress test 2.
• The normal range for respiratory rate at the end of exercise (RRmax) is approximately 36.1 +/- 9.2 breaths per minute for all subjects 2.
• Studies have shown that there is no significant difference in RRmax between men and women 2.
• Tachypnea, or rapid breathing, can be an indicator of various physiological responses to exercise, including increased carbon dioxide output and maximal oxygen uptake 2.

Factors Influencing MRR

• Maximal voluntary ventilation (MVV) manoeuvres have been used to estimate ventilatory capacity and have shown that the longer MVV manoeuvre provides the best estimate of ventilatory capacity 3.
• The relationship between ventilatory capacity, MVV manoeuvres, and respiratory function has been explored, with results indicating that approximately 100% of the ventilatory reserve is used during maximal exercise 3.
• Respiratory muscle strength changes, including decreases in maximal expiratory pressure (PEmax) and maximal inspiratory pressure (PImax), have been observed following maximal and submaximal exercise 4.
• Volitional respiratory muscle training (VRMT) has been shown to improve maximal graded exercise treadmill test performance, including significant decreases in resting supine respiratory rate (RR) and significant increases in total test time (TTT) and derived VO2max 5.

Measurement of MRR

• Respiratory rate at the end of exercise (RRmax) has been measured in various studies, with results indicating a wide range of possible breathing patterns during exercise 2.
• The measurement of RRmax has been correlated with other exercise variables, including carbon dioxide output and maximal oxygen uptake 2.
• The use of MVV manoeuvres to estimate ventilatory capacity has been explored, with results indicating that the longer MVV manoeuvre provides the best estimate of ventilatory capacity 3.